1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera with a view finder. Still more specifically, the invention relates to a single lens camera, the view finder of which displays a true image of the objects to be photographed.
2. Description of the Prior Art
In the course of the history of photography various types of cameras have been proposed varying one from the other by the dimensions of their pictures or by their technical functions. During the previous decades those types differing by their technical functions have developed the view finder camera on the one hand and the reflex camera on the other hand as the two prominent types which both have their respective advantages and disadvantages. The view finder cameras have, as the term already indicates, a view finder through which the motive to be taken is being viewed. The viewfinder image, however, does not give any information regarding the sharp focusing and the depth of focus, as it is not identical with the picture projected on the plane of the film through the lens of the camera. Furthermore, when taking close-up views, parallax errors occur. A particularly serious drawback of the camera with a coincidence-type range finder is the fact that cameras with interchangeable lenses cannot adapt the viewing image to the different angles of the pictures, i.e. the real dimensions of the picture to be taken are not identifiable.
The disadvantages outlined above can be avoided by a reflex camera, classified into two types, i.e. the single lens and the twin lens reflex camera. The twin lens reflex camera provides two lenses co-ordinated to each other, the first of which reproduces the image to be taken on the plane of the film, whereas the other is reproducing a picture of the image on a displaying screen via a surface mirror. The drawback of the twin lens reflex camera is the comparatively high expenditure for lenses and the parallax errors still occuring when taking close-up views.
A picture without parallax errors, the dimensions of which are identical with the picture projected on the plane of the film through any type of lens, is obtainable by the aid of a single lens camera, wherein a picture is projected onto a displaying screen via a surface mirror prior to the exposure, the displaying mirror being in a conjugate plane to the image plane. The mirror mostly is arranged in front of the image plane and produces a laterally inverted picture. In order to obtain a non-reversed picture an erecting prism is arranged between the magnifying lens for the focusing screen and the focusing screen itself. During the exposure, the mirror between the lens of the camera and the plane of the film must be moved away so that the light may pass onto the plane of the film without hindrance. This moving or swinging motion of the mirror is one of the main disadvantages of the single lens reflex camera, as for each exposure the mass of the mirror has to be accelerated and afterwards decelerated. Thus, vibrations are produced and transmitted to the body of the camera which causes blurring at long exposure times. Moreover, the moving of the mirror causes disagreeable noises.
One may dispense with a movable mirror if a partly diaphanous or a beam-splitting prism or mirror is being used (see CANON-Pellix-Camera as described in German Democratic Republic Publication "Fotografie", Leipzig, 1966, No. 6, page 234). Then, however, the light transmittancy is diminished and a reduced light intensity impinges upon the plane of the film. On the other hand, a pentagonal prism is required even for a reflex camera with a still mirror, in order to get an upright picture in the view-finder of the camera.
In the technique of telephoto transmission, however, the dissolution of the picture into picture points and the transmission of the information content of those picture points instead of the transmisson of the picture as a whole has been known for long (cf. British Patent No. 241 636). With the advent of glass fibers or photoconducting fibers this transmission of picture points has been used in various technical fields, e.g. endoscopy (cf. German accepted patent application No. 1 234 920, U.S. Pat. No. 2,975,785). The transmission of colored pictures with or without phase-correction has also been proposed (cf. German published patent application No. 2 317 080; U.S. Pat. Nos. 3,020,806 and 3,449,037).
Furthermore, the advantageous use of light-conducting fibers in the technology of film projection (cf. U.S. Pat. No. 3,143,589, German Utiliy Model No. 77 34 616) as well as in the technology of television (cf. British Pat. No. 1,474,709) has also been known.
Theoretical studies on the qualities and properties of glass fiber pictures have been published by OHZU, SAWATARI and SAYANAGI ("Image Transfer Properties of Fiber Bundle", Japanese Journal of Applied Physics, Vol. 4, Suppl. 1, 1965, p. 323-328), by R. DROUGARD ("Optical Transfer Properties of Fiber Bundles", Journal of the Optical Society of America, Vol. 54, No. 7, p. 907-913) and by E. MARHIC, S. E. SCHACHAM and M. EPSTEIN ("Misalignment in imaging multifibers", Applied Optics, Nov. 1, 1978, Vol. 17, No. 21), for instance.
Finally, glass fibers have also been proposed for still picture as well as moving picture cameras in order to obtain a view finder in a remote position from the camera (cf. Swiss publication "Camera", Bern 1966, Volume 45, issue No. 8, page 52) or to obtainan upright picture in the view finder and to get a simple range finder (see U.S. Pat. No. 3,068,772). In the latter case either side of the objective of the camera comprises a bearing block which supports one end of a bundle of glass fibers arranged behind a lens with a short focal distance. The other end of such a bundle is directed towards the view finder where the ends of the two bundles combine to establish the view finder picture which may be viewed through an eyepiece. To avoid the transmission of one and the same picture by the two respective bundles of glass fibers, the left bundle may be provided for the transmission of the upper part and the right bundle for the transmission of the lower part of the view finder image to be established. Provided that the picture is in focus, both parts of the picture jointlessly coincide as in the case of a cut image range finder. By the aid of an optical system the correspondence of the picture established at the ends of the glass fiber bundles with the picture produced by the objective of the camera on the plane of the film is achieved, but not laterally inverted. If one dispenses with the distance focusing, the known device requires only one bundle of glass fibers by means of which the picture to be taken may be viewed through the view finder (loc.cit.,col. 5, lines 15-21). Although the device described above may do without a mechanical mirror in order to reproduce a picture with a comparatively small parallax in the viewfinder, and although distance measurement is comparatively easy by its aid, it still has various disadvantages. It is, for instance, annoying that the glass fiber bundles are conducted over separate bearing blocks outside the tubus of the camera. Furthermore, the view finder image is not totally devoid of parallax, as the picture projected by the photoconductive fibers is not identical to the picture projected by the objective of the camera. Finally, an additional complicated lens system is required in order to project a picture on the ends of the bundles of the light-conducting fibers in the bearing blocks.
As is known in the art, raster-like transmissions of pictures are not only limited to glass fiber bundles or the like. Instead, in television technology it is common practise to divide a picture into a plurality of elements and to transmit the optical information of each element by time-multiplexing. Of great importance with respect to cameras are opto-electrical converters not comprising any bulky vacuum tubes. Those converters are known as charge-coupled-devices (cf. German published patent application No. 27 34 409; British patent application No. 2 000 416) and MOSTET-devices (cf. British patent application, published under No. 2 001 504) or the like.